The JBL PRX418S is an 18" subwoofer which, when combined with the two-way models, provides a sub/sat system capable of generating 135 dB of full-range, high quality audio. PRX400 passive speakers were designed to provide the sensitivity, frequency response and power handling needed for almost any professional audio environment while still being reasonably  priced. 

Whether you use a powered mixer or an equipment rack full of amps and signal  processing, PRX400 passive speakers deliver the sound power and bandwidth necessary  to make loud music sound natural and even quiet speech intelligible.